Southern California Edison’s decision to permanently shut down the San Onofre Nuclear Station (SONGS) transforms it into a major radioactive waste storage site containing one of the largest concentrations of artificial radioactivity in the United States. These wastes are highly radioactive and will remain dangerous for tensâ€ofâ€thousands of years. According to the U.S. Government Accountability Office (GAO) in testimony before the U.S. Congress in April of this year, spent nuclear fuel is “considered one of the most hazardous substances on earth.”

Over the past 44 years, the San Onofre reactors generated about 948,956 spent fuel rods containing roughly 484 million curies of longâ€lived radioactivity. Of the estimated 1,631 metric tons of spent fuel, about 73 percent is to be stored in two reactor pools. SONGS has generated nearly three times more longâ€lived radioactivity than is stored in some 177 defense highâ€level radioactive tanks at the U.S. Department of Energy’s Hanford site in Washington.

Approximately 43 percent of the intermediate and long-lived radioactivity in the spent nuclear fuel at SONGS is Cesiumâ€137 (Csâ€137). The reactors at San Onofre have generated about 210 million curies of Csâ€137. Of that, about 168 million curies of Csâ€137 are in the two spent fuel pools. By comparison, this quantity of Csâ€137 is more than 6 times the amount released by all atmospheric nuclear weapons tests, and about 89 times that released by the Chernobyl accident.

With a halfâ€life of 30 years, cesiumâ€137 (Csâ€137) gives off potentially dangerous penetrating radiation and is absorbed in the human food chain as if it were potassium. An area roughly two-thirds the size of the state of New Jersey still remains uninhabitable from Csâ€137 released by the Chernobyl nuclear accident in 1986.

According to estimates developed in 2007 for the Nuclear Regulatory Commission’s Emergency Operation Center, for purposes of emergency planning and response, an earthquake at SONGS might cause spent nuclear fuel pool drainage and lead to a catastrophic radiological fire.

Within 6 hours after the water is lost, spent fuel cladding would catch fire releasing approximately 86 million curies of radioactivity into the atmosphere. Of that about 30 percent of the radioactive cesium in the spent fuel (roughly 40 million curies) would escape into the air.

This is 150 percent more than released by all atmospheric nuclear weapons tests. The resulting doses to people living within a 10â€mile radius would be in the lethal range. The pool fire would release far more radioactivity than a reactor meltâ€down. Far less radioactive cesium was released by the Fukushima nuclear disaster, which resulted in significant land and aquatic contaminationâ€resulting in eviction of approximately 150,000 people from their homes, food restrictions, and the large, costly remediation of large areas offsite.

A major reason for this potential hazard is that the pools were meant to store irradiated nuclear fuel no longer than five years and not for indefinite storage of 4â€5 times more than their original designs intended. Thus, U.S. spent nuclear fuel pools are not required to have “defenseâ€indepth” nuclear safety features as required for the reactors. Because they are not under the heavy containment that covers reactor vessels as is mandatory for all new reactors, radiation releases from spent pools are more likely to reach the outside environment.

It will be several decades before a permanent disposal site will be available says the Energy Department’s in its recent strategic plan to implement the Blue Ribbon Commission recommendations. DOE calls for a permanent repository to open in 2048.

This report addresses the potential risks of spent nuclear fuel storage at the San Onofre Nuclear Station (SONGS). Given that more than a half century already passed in the quest for a permanent geological disposal site in the U.S., the State of California should be prepared for the real possibility that spent nuclear fuel will remain on site for decades to come.